It is conventional to mount a rotary switch on the transmission housing externally thereof to receive mechanical gear selection inputs from the operator of a vehicle through various linkages and output gear selections to appropriate output means such as a decoder module and the transmission electronic control unit via electronic signals. The switch includes a quadrant with a selected number of electrical switch segments disposed thereon with each segment providing an output to the output means. The manual valve controlling hydraulic operation of the transmission is mechanically coupled to a plate having indexing detents, called a detent lever, mounted on a shaft and pivotably movable therewith. The shaft extends through the transmission housing wall and a switch bar is fixedly attached to the shaft externally of the transmission housing so that when a vehicle operator selects a gear the switch bar within the rotary switch moves across the quadrant to a predetermined position to engage one or more of the electrical contact segments. In certain systems the electronic control monitors the gear position along with other inputs relative to such things as throttle position, output shaft speed, engine speed, engine load and so on.
In U.S. Pat. No. 5,338,907, assigned to the assignee of the present invention, a switch system is disclosed which is mounted within the transmission housing in order to avoid placing the switches in a hostile environment subject to water splash and the like as well as to avoid tolerance stack-up problems associated with linkages employed when mounting the switches externally of the transmission housing. In that patent a switch housing is shown mounted on the manual lever shaft. The housing is coupled to a roller attached to the detent spring which biases the roller into engagement with the outer edge of the detent lever to maintain the housing stationary relative to the transmission housing. A switch arm fixedly mounted on the manual lever shaft mounts a plurality of first electrical contacts and extends into the switch housing. The switch arm, movable with the detent lever, moves into and out of engagement with respective second electrical contacts mounted on the switch housing. Although transmission fluid can enter and leave the switch housing, suitable seals are provided to prevent ingress of metal particles and other debris into the switch housing. Flexible electrical leads have one end connected to terminals of the electrical contact segments and an opposite end connected to terminals of a connector mounted in a bore provided in the wall of the transmission housing.
Although the switch operates effectively mounted within the transmission housing, a problem can occur during assembly of the transmission in that the electrical leads sometimes are chaffed, pinched or run over a sharp edge thereby causing a short circuit. This problem becomes exacerbated in many newly designed transmissions which tend to be smaller in size.